Conventionally, in a mechanical device including a drive unit composed of an electric motor and a drive mechanism, particularly a mechanical device for industrial machinery, if its operation is stopped for a reason of an abnormality caused by service life or damage of the drive unit, the production activity or physical distribution is stopped. In the circumstances, such a mechanical device is required to predict occurrence of an abnormality, and/or to detect an abnormality at an early or minor stage.
For example, Patent Literature 1 discloses a numeric control device having a failure diagnosis program for determining whether or not values of friction torque and friction force fall within ranges of predetermined permissible values, the values of friction torque and friction force being calculated while a drive mechanism is subjected to a move and stop operation with a unit movement amount in one and the same direction for two or more times, and further to a move and stop operation with the unit movement amount in the opposite direction for two or more times.
Further, for example, Patent Literature 2 discloses a rotator bearing diagnostic device comprising: a vibration waveform database that stores a vibration waveform of a bearing of a rotator rotated by a motor; feature frequency extracting means that extract a vibration component of a theoretical frequency corresponding to a target-device specification from FFT analysis on the vibration waveform; statistic calculating means that calculate a mean value and a standard deviation from the extracted frequency amplitude; criterion calculating means that calculate a criterion from the calculated statistic; and determining means that determine whether there is an abnormality in the rotator by comparing the vibration waveform with the criterion.